The company is booming in the virtual reality business on the back of a game called Zombie Outbreak, about slaughtering zombies in a virtual reality world, which is run out of its South Melbourne base.

Zombie slayer: Kelly had no clue what was to come. Picture: Supplied

It's there that Alex took his zombie-obsessed girlfriend Kelly last weekend, telling her he wanted to slay virtual zombies as a present for his upcoming birthday.

What she didn't know was that he'd been in touch with Zero Latency four weeks before, asking them to help out with a virtual reality wedding proposal.

Initially, it was thought creating such exhaustive custom content would be too big an ask.

Then Zero Latency's chief technology officer Scott Vandonkelaar got wind of the request, got excited, and they agreed to give it a shot.

"We wanted to do it because we love making experiences that excite people and make them happy," Scott said.

"It was a great opportunity to show what virtual reality can do - it's not just games."

Alex's original vague plan of emerging from a virtual zombie apocalypse to propose as they played took a more romantic turn when Scott asked him what Kelly's favourite place was.

Alex doesn't know how to code virtual reality, but he knows what makes Kelly tick.

He knew the tree out front of her grandmother's place in South Africa was the place.

"Every time she thinks of her happiest place she thinks of the time she spent out there with her friends and her family as a kid," Alex says.

The real tree Kelly remembers from her childhood. Picture: Supplied.

Kelly's parents and sisters live in Australia, but the rest of the family is there, so he wanted a way to make her feel like she was surrounded by family as he proposed.

Several pictures, a lot of coding, and two weeks of work later, Zero Latency knew they were able to transport her - virtually - to her happy place.

Fast forward to last weekend, and Kelly and Alex happily blasting away at virtual zombies with a bunch of other Zombie Outbreak players.

Suddenly, her headset "reboots" and teleports her to her favourite place in the world - the virtual reality construction of the tree outside her grandmother's place in South Africa.

At this point, Scott confesses, the only person more nervous than him was probably Alex: would she recognise - and connect with - his team's creation?

The moment. Picture: Supplied

Kelly's incredulous "what ... is that my grandmother's house" saw him breathe a sigh of relief.

In reality, another step and she would have gone headlong into the warehouse wall, Alex laughs.

The video of the moment shows "virtual" Alex grabbing "virtual" Kelly's hand and they take in the scene before he says: "I know we've had a joke where we 'virtually feel like we're already engaged, so I thought why not make that a reality," and drops down on one knee.

Finally, the penny drops, and Kelly realises there's a proposal about to happen, takes her headset off, and receives her marriage proposal in real life.

Reality and virtual reality collide. Picture: Supplied

He sprung the ultimate surprise - even managing to get friends and family (real, live ones) to the warehouse to watch it unfold.

"It was awesome because she was totally in her world, shooting zombies, and then it all changed," he says.

Kelly was so distracted by being to transported to her grandmother's house, she had no idea Alex was going to ask her to marry him.

"In hindsight, yeas, it's obvious ... why am I holding flowers ... but it took a while to register," she said.

"It was this moment when I just got to go home for a few seconds.

"But once I realised it was happening I needed to see him for real".

For the record, the engagement ring Alex slips on Kelly's finger is also real.

As is the kiss that seals the deal. And the February 2018 wedding date.

Although Kelly has speculated that down the track, virtual reality childbirth could prove a little easier than the real thing!